[Discuss-gnuradio] PSK mod/demod: errors in the first 50 bytes (was: Re: (no subject))

[Marcus Müller]

Hi Shriharsha,

As Zakaria already pointed out, since real channels are imperfect,
packet losses *must* occur.
The demod will need some samples to lock on to your rx signal, so losses
at start are to be expected.

I can only point you to some reference:
there is a GNU Radio Companion file in
gnuradio/gr-digital/examples/demod/ called dpsk_loopback.grc . That
should work.
You can insert a channel model in between mod and demod, and see what
happens. Increase channel influences (noise power, etc.) until they
match or exceed
what you'd expect from your real-world channel.
Later, split the flowgraph in halves and connect them to your USRP
sink/sources (don't forget to remove the throttle at that point).

Greetings,
Marcus

PS: For the future, when asking a question, please try to apply the
hints from
http://gnuradio.org/redmine/projects/gnuradio/wiki/ReportingErrors .
This will make it much easier to help you :)
On 24.05.2014 18:51, zielalaoui wrote:
> hello SHRIHARSHA,
> If your simulation looks good, try and see what's different about the
> incoming signal on air as opposed to the simulation. Is the frequency offset
> maybe too large? Is the received amplitude correct? Try mapping these into
> your simulation and see where things start to fall apart. At this point, you
> seem to have the basic setup correct and just need to continue to experiment
> with the settings.
> The packet decoder will work pefectly if the input signal of the demodulator
> is good enough. The sample rate is also an issue, you should find the best
> value for your application.
> Zakaria
>
>
>
>
> --
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